Avoid httpretty version 0.8.3

Installation of httpretty 0.8.3 fails in environments with LC_ALL=C
(e.g. from tox) with the following error: UnicodeDecodeError: 'ascii' codec
can't decode byte 0xc3 in position 133: ordinal not in range(128)

The patch puts problem version into black list.

Change-Id: Ic0e0a37ef3c0994fa6cb4cb6b1b7f06700fcbf29
Merge "Avoid httpretty version 0.8.3"